Expandable Trials

ABSTRACT

An expandable implant is made via a central strut having a pivotable arm on each end. The implant can be inserted into a disc space either horizontally or vertically with the arms in a closed position and then (if inserted horizontally) optionally rotated up into place. The arms are then pivoted out, thereby increasing the foot print of a horizontally inserted implant. The expanded implant can be locked in place through the use of an additional insert or ratchet that fits between the arms and locks the arms in place.

CONTINUING DATA

This patent application claims priority from US provisional applicationU.S. Ser. No. 62/329,589, filed Apr. 29, 2016 entitled “ExpandableTrials” (Bootwala et al.) (DSP5202USPSP1), and from US provisionalapplication U.S. Ser. No. 62/239,336, filed Oct. 9, 2015 entitled“Expandable Trials” (Bootwala et al.) (DSP5202USPSP), the specificationsof which are incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

The leading cause of lower back pain arises from rupture or degenerationof lumbar intervertebral discs. Pain in the lower extremities is causedby the compression of spinal nerve roots by a bulging disc, while lowerback pain is caused by collapse of the disc and by the adverse effectsof articulation weight through a damaged, unstable vertebral joint. Oneproposed method of managing these problems is to remove the problematicdisc and replace it with a prosthetic disc that allows for the naturalmotion between the adjacent vertebrae (“a motion disc”).

Prior to inserting the disc, however, the surgeon typically desires toinsure that the properly sized implant has been identified for theparticular patient. To this end, trial implants are commonly includedwithin the instrument sets that allow the surgeon to temporarily insertthe trial into the intervertebral disc space and assess whether theheight and footprint of the trial would be appropriate for the actualimplant to be inserted. Typically, a large number of trials are suppliedin an instrument set, with each having a distinct height, lordotic angleand footprint.

More recently, fusion cages have been redesigned to provide a smallprofile during insertion into the disc space and then to expand todistract the disc space. The small profile of the initial configurationallows the surgeon to operate through a smaller opening, therebyminimizing surgical trauma. With the advent of these expandable cages,there is now also a need for an expandable trial as well.

SUMMARY OF THE INVENTION

In one embodiment, an expandable implant is made via a central struthaving a pivotable arm on each end. The implant can be inserted into adisc space either horizontally or vertically with the arms in a closedposition and then (if inserted horizontally) optionally rotated up intoplace. The arms are then pivoted out, thereby increasing the foot printof a horizontally inserted implant. The expanded implant can be lockedin place through the use of an additional insert or ratchet that fitsbetween the arms and locks the arms in place.

DESCRIPTION OF THE DRAWINGS

FIGS. 1-4 disclose a multi-plate expandable device.

FIG. 5 discloses a spreader-based expandable device.

FIGS. 6-14 disclose expandable devices based upon stackable blocks.

FIGS. 15-20 disclose spring-based expandable designs.

FIGS. 21-22 disclose an ellipse-based expandable design.

FIGS. 23-28 disclose an expandable device based upon floating blades.

FIGS. 29-31 disclose an expandable device based upon gears.

FIGS. 32-38 disclose an expandable design based upon a box chisel.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with FIGS. 1-4, there is provided an intervertebraldevice, comprising:

-   -   a) a first strut 1 comprising i) an upper portion 3 forming an        upper surface 5 having teeth 7 adapted for gripping an upper        natural endplate and ii) a lower portion 9 forming a lower        surface 11 comprising teeth 13 adapted for gripping a lower        natural endplate,    -   b) an upper arm 15 pivotally connected to the upper portion of        the first strut and having an upper surface 17 having teeth 18        adapted for gripping an upper natural endplate, and    -   c) a lower arm 19 pivotally connected to the lower portion of        the first strut and having a lower surface 21 having teeth 23        adapted for gripping a lower natural endplate,    -   wherein the upper surface of the first strut and the upper        surface of the upper arm are substantially co-planar in an        expanded condition,    -   wherein the lower surface of the first strut and the lower        surface of the lower arm are substantially co-planar in an        expanded condition.        -   Preferably, the pivotal connections between first strut and            each arm each form a ratchet connection 25 adapted to lock            the device in the expanded condition.

In some embodiments, the device further comprises:

-   -   d) a second strut 27 extending between a lower surface of the        upper arm and an upper surface of the lower arm to lock the        device in the expanded condition.        -   Preferably, each of the lower surface of the upper arm and            the upper surface of the lower arm comprises a recess 29            adapted for reception of a respective end of the second            strut.    -   Preferably, each arm has a first endface 31 opposite its pivotal        connection, and the first endfaces are substantially opposed in        an unexpanded condition.

Also in accordance with FIGS. 1-4, there is provided: a method of usingan intervertebral device, comprising the steps of:

-   -   a) inserting the intervertebral device of claim 1 into a disc        space in its unexpanded condition,    -   b) moving each arm so that the device adopts its expanded        condition,    -   c) locking the device in its expanded condition.

Footprint/Spreader

In a FIG. 5 embodiment, there is provided a spreader trial in which aU-shaped element houses a spreader having a substantially rectangularaxial cross-section, wherein the height of the cross-section is lessthan its width. The spreader is rotatably coupled to the apex of theU-shaped element. These two elements are inserted into the disc space asone piece, with a rotatable shaft carrying the spreader and coupled tothe apex of the U-shaped element. The U-shaped element is inserted sothat each leg of the U-shaped is substantially parallel to the adjacentvertebral endplates (i.e., the U-shaped spreader cross-section providesa minimum height), while the spreader is inserted so that its height isextending between the endplates and a minimum height is established.Once inserted, the shaft is rotated about 90 degrees so that thespreader width is now extending between the endplates so that thespreader displays its maximum height. This condition preferably producesdistraction of the disc space. Bone filler can then be added around thespreader within the U-shaped element.

In accordance with FIG. 5, there is provided an intervertebral devicecomprising:

-   -   a) a substantially U-shaped element 33 comprising a        substantially C-shaped portion 35 and a pair of arms 37        extending therefrom, an upper surface 39 adapted for gripping a        natural endplate, a lower surface 41 adapted for gripping a        natural endplate, and an inner surface 43 including a concave        surface 45, the concave surface having a first threaded coupling        extending therein, wherein the inner surface defines a cavity,        wherein a first distance between the upper and lower surfaces        defines a first height, and wherein a second distance between        the inner surfaces of the arms defines a width of the cavity,    -   b) a spreader element 51 having i) a block 53 having a first end        55 having a second threaded coupling 57 that mates with the        first threaded coupling, a second end 59, a second height and a        width, wherein the height is less than the width, ii) a shaft 61        extending from the second end of the block and iii) a handle        (not shown) connected to the shaft,        wherein the first and second threaded couplings threadably mate,        wherein the width of the block is less than the width of the        cavity so that the block of the spreader element is received in        the cavity of the U-shaped element.

Also in accordance with FIG. 5, there is provided a method of preparinga disc space between opposed vertebral endplates, comprising the stepsof:

a) inserting the intervertebral device of FIG. 5 into a disc spacewherein the block is oriented so that the height of the block spans theopposed vertebral endplatesb) rotating the block by about 90 degrees so that the width of the blockspans the opposed vertebral endplates, thereby distracting the discspace.

Preferably, this method further comprises the steps of:

-   -   c) disengaging the spreader from the U-shaped element, and    -   d) removing the block from the disc space.

Also preferably, this method further comprises the steps of:

-   -   e) contacting the U-shaped element with an implant material.

Stackable Blocks

In a FIGS. 6-9 embodiment, a plurality of stackable spacers are insertedin sequence to build an implant of a desired height and preferablywidth. Preferably, the spacers are designed so that the subsequentspacers can be added both in the vertical and lateral directions.Preferably, endcap spaced are also utilized that cap off the verticaldimension and provide lordosis. In one embodiments, the endcaps havevertical throughholes and legs extending towards each other that aredesigned to mate, so that once the endcaps are placed and mated, theintermediate spacers can be removed and a hollow fusion cage results.

In accordance with FIGS. 6-9, there is provided an intervertebral devicecomprising:

-   -   a) a base block 65 having an upper surface 67 having a first        mating feature 69, a lower surface 71 and a first side surface        73 having a second mating feature 75 therebetween,    -   b) a first upper spacer 77 having a lower surface 79 having a        third mating feature 81, and an upper surface 83 having a fourth        mating feature 85, and a side surface 87 therebetween    -   c) a first lateral spacer 89 having an inner side surface 91        having a fifth mating feature 93, an outer side surface 95        having a sixth mating surface 97 therebetween, and an upper        surface 99 therebetween,        wherein the first mating feature of the base block slidably        mates with the third mating feature of the first upper spacer,        and        wherein the second mating feature of the base block slidably        mates with the fifth mating feature of the first lateral spacer.

In some embodiments, each mating feature is a dovetail feature.

Preferably, the device further comprises:

-   -   d) a second upper spacer 101 having a lower surface 103 having a        seventh mating feature 105, and an upper surface 107 having a        eighth mating feature 109, and a side surface 111 therebetween    -   e) a second lateral spacer 113 having an inner side surface 115        having a ninth mating feature 117, an outer side surface 119        having a tenth mating surface 121 therebetween, and an upper        surface 123 therebetween,        wherein the fourth mating feature of the first upper spacer        slidably mates with the seventh mating feature of the second        upper spacer, and        wherein the sixth mating feature of the first lateral spacer        slidably mates with the ninth mating feature of the second        lateral spacer.

Preferably, the device further comprises:

-   -   f) a third upper spacer having a lower surface having an        eleventh mating feature, an upper surface disposed at an angle        to its lower surface, and a side surface therebetween,    -   wherein the third upper spacer is disposed above the second        vertical spacer.

Preferably, the eleventh mating feature of the third vertical spacer islocated substantially directly above the eighth mating surface of thesecond vertical spacer.

FIG. 10 discloses a central insert 65 within the stackable blocks.

Also in accordance with FIGS. 11-12, there is provided other stackabledesigns with various inserts 65.

In a FIG. 13a -14 embodiment, there is an intervertebral devicecomprising:

-   -   a) an upper shell 171 having an upper surface 173 having a        throughhole 175 therethrough and opposed sidewalls,    -   b) a lower shell 177 having a lower surface 179 having a        throughhole 181 therethrough and opposed sidewalls,    -   c) a plurality of stacked spacers disposed between the upper        shell and the lower shell, wherein each spacer shares with its        adjacent spacer a mating interface comprising a pair of mating        features,    -   wherein the opposed sidewalls of the upper shell mate with the        opposed sidewalls of the lower shell.

In some embodiments, there is a method of building a fusion cagecomprising:

-   -   inserting into a disc space a plurality of stacked spacers,        wherein each spacer shares with its adjacent spacer a mating        interface comprising a pair of mating features, the plurality        having an uppermost spacer having an upper mating feature and a        lowermost spacer having a lower mating feature,    -   attaching to the uppermost spacer an upper shell having an upper        surface having a throughhole therethrough, a lower surface        having a lower mating feature and opposed sidewalls, wherein the        upper mating feature of the uppermost spacer mates with the        lower mating feature of the upper shell,    -   attaching to the lowermost spacer a lower shell having an lower        surface having a throughhole therethrough, an upper surface        having an upper mating feature and opposed sidewalls, wherein        the lower mating feature of the lowermost spacer mates with the        upper mating feature of the lower shell,    -   attaching the sidewalls of the upper shell to the sidewalls of        the lower shell,    -   removing the plurality of stacked spacers from the disc space to        create a void between the upper and lower shells, and    -   filling the void with a bone filler.

FIG. 14 discloses trial heights sections with the links section 178. Asthe clinician pushes the trial sections forward, they will ride up theramps of each other with the aid of link sections holding them alltogether. As the trail sections are stacked, this will determine thedisc height for the appropriate implant.

Spring

In the FIG. 15 embodiment, a torsion spring is provided between implantendplates in a collapsed configuration having a height H1. Once thetension in the spring is released, the spring expands, therebyincreasing the height between the endplates to an expanded height H2.The torsion spring could also be made from one or more nitinol leafsprings that expand through temperature change or mechanical means. Oncethe implant is expanded, the spaced between the endplates can be filledwith bone graft or a monolithic insert.

In accordance with FIG. 15, there is provided:

-   -   an intervertebral device comprising;    -   a) a first endplate 201 having an outer surface 203 adapted for        gripping a first natural endplate and an inner surface 205,    -   b) a second endplate 207 having an outer surface 209 adapted for        gripping a second opposed natural endplate and an inner surface        211,    -   c) a torsion spring 213 having a first portion 215 contacting        the inner surface of the first endplate and a second portion 217        contacting the inner surface of the second endplate,        the device having an unexpanded state and an expanded state,        wherein the torsion spring is tensioned in the unexpanded state        and released in the expanded state.

Also in accordance with FIG. 16, there is provided an intervertebraldevice comprising;

-   -   a) a first endplate 219 having an outer surface 221 adapted for        gripping a first natural endplate and an inner surface 223,    -   b) a second endplate 225 having an outer surface 227 adapted for        gripping a second opposed natural endplate and an inner surface        229,    -   c) a memory metal leaf spring 231 having end portions contacting        the inner surface of the first endplate and an intermediate        portion 233 contacting the inner surface of the second endplate,        the device having an unexpanded state and an expanded state,        wherein the leaf spring is under force in the unexpanded state        and released in the expanded state.

In a FIG. 17-18 embodiment, tethers are used to hold a coil spring in acollapsed state so that an implant has a collapsed height H1. Thetethers can be cut or removed after insertion, thereby allowing theimplant to expand under spring tension to a height H2. The space betweenthe endplates can be filled with bone graft or a monolithic insert. Thetension of the spring can be adjusted by using different springs.

In one embodiment, three springs increasing force are providedsequentially between endplates. The release of the varying tensions inthe springs produces lordosis. Additionally, the expanded endplates canbe held open in all of these spring embodiments through a mechanicalmeans such as a cam locking mechanism.

In accordance with FIGS. 17-18, there is provided an intervertebraldevice comprising;

-   -   a) an upper endplate 235 having an upper surface 237 adapted for        gripping an upper natural endplate and a lower surface 238,    -   b) a lower endplate 239 having a lower surface 241 adapted for        gripping a lower natural endplate and an upper surface 243,    -   c) a coil spring 245 having a first endportion 247 contacting        the lower surface of the upper endplate and a second endportion        249 contacting the upper surface of the lower endplate,    -   d) a tether 251 having a first endportion 253 contacting the        lower surface of the upper endplate and a second endportion 255        contacting the upper surface of the lower endplate,        the device having an unexpanded state and an expanded state,        wherein the coil spring is tensioned in the unexpanded state and        released in the expanded state,        wherein the tether is tensioned in the unexpanded state and        severed in the expanded state.

In accordance with FIGS. 19-20, there is provided an intervertebraldevice comprising;

-   -   a) A first endplate 261 having an outer surface 263 adapted for        gripping a first natural endplate, an inner surface 265, an        anterior end 267 and a posterior end 269,    -   b) a second endplate 271 having an outer surface 273 adapted for        gripping a second opposed natural endplate, a lower surface 275,        an anterior end 277 and a posterior end 279,    -   c) a first coil spring 281 having a first endportion 283        contacting the inner surface of the first endplate and a second        endportion 285 contacting the inner surface of the second        endplate,    -   d) a second coil spring 287 having a first endportion 289        contacting the inner surface of the first endplate and a second        endportion 291 contacting the inner surface of the second        endplate,        wherein a first distance between the outer surfaces at the        anterior ends of each endplate constitutes an anterior height,        and wherein a second distance between the outer surfaces at the        posterior ends of each endplate constitutes a posterior height,        and        the device having an unexpanded state and an expanded state,        wherein each coil spring is tensioned in the unexpanded state        and released in the expanded state,        wherein the first and second coil spring provide varying        tensions so that, in the released state, the anterior height is        smaller than the posterior height.

Ellipse

This FIGS. 21-22 embodiment has an elliptical body housed between twoendplates. The ellipse has two opposed arcuate slots on its face thatmate with a pair of pins placed substantially in the center of eachendplate. A pair of springs are also provided between the two endplateson either side of the ellipse. These springs are compressed in thecollapsed state of the implant. When the springs are release, they pushthe endplates apart and the ellipse rotates in accordance with thetravel of the pins in the slots, thereby producing an expanded state forthe implant.

In accordance with FIGS. 21-22, there is provided an intervertebraldevice comprising:

-   -   a) an upper endplate 301 having an upper surface 303 and an        upper pin 305 extending therefrom in a direction substantially        parallel to the upper surface,    -   b) a lower endplate 307 having a lower surface 309 and a lower        pin 311 extending therefrom in a direction substantially        parallel to the lower surface,    -   c) first and second compression springs 313, each spring having        an upper endportion 315 attached to the upper endplate and a        lower endportion 317 attached to the lower endplate,    -   d) a substantially elliptical body 319 disposed between the        upper and lower endplates and between the first and second        springs, the body having:        -   i) a first dimension defining a height, a second dimension            perpendicular thereto defining a width, wherein the height            is greater than the width, a center, and a perimeter,        -   ii) an upper arcuate slot 321 therethrough and a lower            arcuate slot 323 therethrough, and        -   iii) an actuation element 327 for rotating the body,    -   wherein the upper pin is slidingly received in the upper arcuate        slot and the upper pin is slidingly received in the upper        arcuate slot,    -   wherein the device has a collapsed state and an expanded state,    -   wherein, when the device is the collapsed state, the body        extends between the endplates substantially in the second        dimension and the springs are in compressed states, and    -   wherein, when the device is the expanded state, the body extends        between the endplates substantially in the first dimension and        the springs are in expanded states.        -   Preferably, the actuation element is a projection disposed            substantially in the center of the substantially elliptical            body.        -   Preferably, the actuation element is a recess disposed            substantially in the center of the substantially elliptical            body.        -   Preferably, the actuation element has a hexagonal shape and            is disposed substantially in the center of the substantially            elliptical body.        -   Preferably, the upper endplate has an upper pawl 329 and the            body has an upper ratchet 331 upon its perimeter, wherein            the upper pawl is engaged with the upper ratchet.            preferably, the lower endplate has a lower pawl 333 and the            body has a lower ratchet 335 upon its perimeter, wherein the            lower pawl is engaged with the lower ratchet,        -   Preferably, the upper and lower pins extend substantially in            the same direction.        -   Preferably, the upper and lower pins each extend            substantially in the same direction.        -   Preferably, each endplate has first 336 and second 337 ends            and each pin is located approximately halfway between the            first and second ends.

Squid

In this FIG. 23-25 d embodiment, an inserter having upper and lowerflexible blades is provided. A shaft with a pusher at its end isadvanced between the blades. The pusher has an acicular cross-section sothat its height is less than its width. Rotation of the pusher causesthe larger width of the pusher to extend between the endplates therebydistracting the disc space. An indicator is built in to the inserterthat measures the amount of distraction and thus the height.

In some embodiments, the shaft can be retracted and an implant loaded infront of the pusher. The shaft can then be advanced to act as aninserter.

-   -   In accordance with FIGS. 23-25 d, there is provided an        intervertebral implant inserter, comprising:    -   a) a elongated central body 341 having a distal end 343, a        proximal end, an outer surface, and a longitudinal throughbore        349 therethrough,    -   b) upper 351 and lower 353 blades, each blade having a distal        end portion 355 and a base portion 357, the base portion of each        blade pivotally coupled to the elongated central body,    -   c) a shaft 359 having a longitudinal axis, wherein the shaft is        advanceable within the throughbore and rotatable about the        longitudinal axis, the shaft having a distal end 361 forming a        pusher 363 having an acicular transverse cross-section,    -   d) upper 365 and lower 367 endplates respectively detachably        connected to the distal end portion of a respective blade.

Preferably, each endplate has an upper surface 369, a lower surface 371,and a central throughhole 373 extending from the upper surface to thelower surface.

Preferably, the inserter further comprises:

e) a height indicator 375 attached to the elongated central body.

In some embodiments, there is an intervertebral assembly comprising:

a) the inserter of FIG. 23, andb) a spacer disposed between the endplates and having an upper surface,a lower surface, and vertical throughhole extending between its upperand lower surfaces.

Preferably, the upper surface of the spacer is substantially uniplanarwith the upper surface of the upper endplate, and the lower surface ofthe spacer is substantially uniplanar with the lower surface of thelower endplate.

-   -   Preferably, the vertical throughhole of the spacer substantially        aligns with the central throughhole of each endplate.

In some embodiments, there is provided an intervertebral assemblycomprising:

-   -   a) the inserter of FIG. 23, and    -   b) a spacer disposed distal of and in contact with the pusher,        the spacer having an upper surface, a lower surface, and        vertical throughhole extending between its upper and lower        surfaces.

Reverse Squid

In the FIG. 26-28 embodiment, a core is provided between two rampedsurfaces and caused to move between them, thereby increasing thedistance between the two ramped surfaces. As the knob of the device isturned, the knob pulls the cable proximally, thereby pulling wedged coreproximally as well. An indicator on the cable indicates the heightachieved by the activity. In some embodiments, a second core is providedthat indicates the angle of lordosis. In some embodiments, the rampedsurfaces have indents or other such markings that provide heightincrements. In some embodiments, a spring is wrapped around the distalend portion of the cable, thereby allowing retraction of the core andbring the device back to its collapsed state.

-   -   In other embodiments, a wedged core is advanced forward instead        of being retracted to allow for indications of height and        lordotic angle.

In accordance with FIGS. 26-28, there is provided, an intervertebraltrial, comprising;

-   -   a) an upper endplate 381 having a proximal end portion 383, a        distal end portion 385, an upper surface 387 and a lower surface        389 disposed at an acute angle from the upper surface,    -   b) a lower endplate 391 having a proximal end portion 393, a        distal end portion 395, a lower surface 397 and an upper surface        399 disposed at an acute angle from the lower surface,    -   c) a tube 401 having a throughbore 403, a proximal end portion        405, and a distal end portion 407 pivotally attached to the        proximal end of each endplate    -   d) a spacer 409 disposed between a the distal end portions of        the endplates and biased against the lower surface of the upper        endplate and the upper surface of the lower endplate,    -   e) a cable 411 having a distal end portion 412 attached to the        spacer, an intermediate portion 413 disposed within the        throughbore of the tube, and a proximal end portion 415,    -   f) a knob 417 threadably attached to the proximal end portion of        the tube and connected to the proximal end portion of the cable,    -   g) an indicator 419 extending from the cable, and    -   h) a first indicia of distance 421 attached to the tube and        adapted to measure changes of position of the indicator.        wherein proximal movement of the cable causes the spacer to move        proximally, thereby causing the upper surface of the upper        endplate and lower surface of the lower endplate to move apart a        distance that is conveyed by the viewing the indicator against        the first indicia of distance.

Preferably, the trial further comprises:

-   -   i) a spring 423 disposed about the distal end portion of the        cable.    -   Preferably, at least one of the lower surface of the upper        endplate and the upper surface of the lower endplate comprises a        second indicia of distance.    -   Preferably, the upper surface of the upper endplate and the        lower surface of the lower endplate are substantially parallel.

Now referring to FIG. 27, as the ball 409 is pulled back, the ball willrest in the indents 400 within the trail arms. The small indents arespaced apart for different trail heights. The ball position willindicate the heights on the disk space.

Gears

Now referring to FIGS. 29-31, there is provided an expandableintervertebral device in which two sets of parallel flanges are pivotedfrom a collapsed configuration in opposite directions about 90 degreesto produce an expanded configuration capable of distracting a discspace. In some embodiments, the sets of flanges are attached on oppositesides of a fixed carriage. The opposite pivoting of the flanges (i.e.,clockwise and counterclockwise) is accomplished by rotating a pair ofinterlocked gears respectively connected to the first and secondflanges. The rotation can be accomplished by inserting a driver into adriving connection on one of the gears and rotating the driver to causeopposed rotation of the gears and thereby opposed pivoting of the setsof flanges. The pivoting can be stopped and locked after the desiredamount of distraction is achieved.

In some embodiments, the device is used as a trial to measure the amountof distraction, preferably as a prelude to inserting an expandable cage.The amount of distraction can be measured by measuring the amount ofgear rotation. If the expandable cage has a lordotic feature, then theratio of the gear diameters can be less than one to provide the requiredlordosis. Accordingly, the amount of angle produced can also be measuredby measuring the extent of rotation in these different diameter gears.

In some embodiments, both gears can operate independently of each otherby the use of a toggle switch in order to obtain precise angulation ofthe spacer.

In accordance with FIGS. 29-31, there is provided: an intervertebraldevice comprising:

-   -   a) a first elongate flange 431 having a first end portion 433, a        second end portion 435 and a pair of lateral sidewalls 437,    -   b) a second elongate flange 439 having a first end portion 441,        a second end portion 443 and a pair of lateral sidewalls 445,    -   c) a first gear 447 connected to the first flange by a first pin        449, the first gear having a plurality of teeth 451 and a        driving connection 453,    -   d) a second gear 455 connected to the second flange by a second        pin 457, the second gear having a plurality of teeth 459,    -   e) a carriage 461 comprising a proximal wall 463 having first        and second throughholes extending in the proximal-distal        direction, a distal wall 469 and a bottom wall 471 connecting        the proximal and distal walls, wherein the bottom wall has a        bottom surface 473,    -   wherein the teeth of the first and second gears are interlocked,    -   wherein the first and second pins respectively pass through the        first and second throughholes and respectively connect to the        first end portions of the first and second flanges,    -   wherein the device has a collapsed configuration in which the        sidewalls of the elongate flanges are substantially parallel to        the bottom surface,    -   wherein rotation of the gears in the collapsed configuration        produces in the device an expanded configuration in which the        sidewalls of the elongate flanges are substantially        perpendicular to the bottom surface.    -   Preferably, the device further comprises:    -   f) a third elongate flange 475 having a first end portion 477, a        second end portion 479 and a pair of lateral sidewalls 481,    -   g) a fourth elongate flange 483 having a first end portion 485,        a second end portion 487 and a pair of lateral sidewalls 489,        wherein the first and second pins respectively pass through the        first and second flanges and respectively connect to the first        end portions of the third and fourth flanges, thereby        respectively connecting the first and second pins to the third        and fourth flanges,        wherein the first and third elongate flanges are substantially        parallel in the collapsed and expanded configurations,        wherein the second and fourth elongate flanges are substantially        parallel in the collapsed and expanded configurations,    -   Preferably, each flange has a second end and wherein, in an        expanded configuration, a distance between the bottom surface of        the bottom wall of the carriage and the second end of each        flange corresponds substantially to the height of a disc space.    -   Preferably, each flange comprises a narrowed intermediate        section 493 between the first and second end portions.

Box Chisel

In the FIG. 32-38 embodiment, a four-sided osteotome is modified tohouse a pair of endplates connected by an expansion mechanism. In use,the osteotome is used as a box chisel to shape the disc space, and thenthe expansion mechanism is actuated to eject the endplates away from therest of the osteotome, thereby providing a basis for an implant.

-   -   In accordance with FIGS. 32-38, there is providedan expandable        intervertebral box chisel, comprising;    -   a) a four-sided osteotome 501 comprising i) an upper wall 503        having a vertical throughhole 505 and a sharpened distal edge        507 and ii) a lower wall 509 having a vertical throughhole and a        sharpened distal edge 513, and iii) opposed sidewalls 515        connected the upper and lower walls,    -   b) a shaft 517 having a proximal end portion 519 and a distal        end portion 521 connected to the osteotome,    -   c) a handle 523 connected to the proximal end portion of the        shaft, and    -   d) upper 525 and lower endplates disposed in the respective        vertical throughholes and connected by an expansion mechanism        529,        wherein the chisel has a collapsed configuration in which the        endplates are disposed in the throughholes and separated by a        first distance and an expanded configuration in which the        endplates are moved further apart and out of the throughholes,        and are separated by a second distance greater than the first        distance.    -   Preferably, the expansion mechanism comprises a spring.    -   Preferably, the expansion mechanism comprises a ratchet.    -   Preferably, the upper and lower walls are pivotally attached at        a first pivot junction proximal to the osteotome.

We claim:
 1. An intervertebral device, comprising: a) a first strutcomprising i) an upper portion forming an upper surface having teethadapted for gripping an upper natural endplate and ii) a lower portionforming a lower surface comprising teeth adapted for gripping a lowernatural endplate, b) an upper arm pivotally connected to the upperportion of the first strut and having an upper surface having teethadapted for gripping an upper natural endplate, and c) a lower armpivotally connected to the lower portion of the first strut and having alower surface having teeth adapted for gripping a lower naturalendplate, wherein the upper surface of the first strut and the uppersurface of the upper arm are substantially co-planar in an expandedcondition, wherein the lower surface of the first strut and the lowersurface of the lower arm are substantially co-planar in an expandedcondition.
 2. The device of claim 1 wherein the pivotal connectionsbetween first strut and each arm each form a ratchet connection adaptedto lock the device in the expanded condition.
 3. The device of claim 1further comprising: d) a second strut extending between a lower surfaceof the upper arm and an upper surface of the lower arm to lock thedevice in the expanded condition.
 4. The device of claim 3 wherein eachof the lower surface of the upper arm and the upper surface of the lowerarm comprises a recess adapted for reception of a respective end of thesecond strut.
 5. The device of claim 1 wherein each arm has a firstendface opposite its pivotal connection, and the first endfaces aresubstantially opposed in an unexpanded condition.
 6. A method of usingan intervertebral device, comprising the steps of: a) inserting theintervertebral device of claim 1 into a disc space in its unexpandedcondition, b) moving each arm so that the device adopts its expandedcondition, c) locking the device in its expanded condition.
 7. Anintervertebral device comprising: a) a substantially U-shaped elementcomprising a substantially C-shaped portion and a pair of arms extendingtherefrom, an upper surface adapted for gripping a natural endplate, alower surface adapted for gripping a natural endplate, and an innersurface including a concave surface, the concave surface having a firstthreaded coupling extending therein, wherein the inner surface defines acavity, wherein a first distance between the upper and lower surfacesdefines a first height, and wherein a second distance between the innersurfaces of the arms defines a width of the cavity, b) a spreaderelement having i) a block having a first end having a second threadedcoupling that mates with the first threaded coupling, a second end, asecond height and a width, wherein the height is less than the width,ii) a shaft extending from the second end of the block and iii) a handleconnected to the shaft, wherein the first and second threaded couplingsthreadably mate, wherein the width of the block is less than the widthof the cavity so that the block of the spreader element is received inthe cavity of the U-shaped element.
 8. A method of preparing a discspace between Opposed vertebral endplates, comprising the steps of: a)inserting the intervertebral device of claim 1 into a disc space whereinthe block is oriented so that the height of the block spans the opposedvertebral endplates b) rotating the block by about 90 degrees so thatthe width of the block spans the opposed vertebral endplates, therebydistracting the disc space.
 9. The method of claim 8 further comprisingthe steps of: c) disengaging the spreader from the U-shaped element, andd) removing the block from the disc space.
 10. The method of claim 9further comprising the steps of: e) contacting the U-shaped element withan implant material.
 11. An intervertebral device comprising: a) a baseblock having an upper surface having a first mating feature, a lowersurface and a first side surface having a second mating featuretherebetween, b) a first upper spacer having a lower surface having athird mating feature, and an upper surface having a fourth matingfeature, and a side surface therebetween c) a first lateral spacerhaving an inner side surface having a fifth mating feature, an outerside surface having a sixth mating surface therebetween, and an uppersurface therebetween, wherein the first mating feature of the base blockslidably mates with the third mating feature of the first upper spacer,and wherein the second mating feature of the base block slidably mateswith the fifth mating feature of the first lateral spacer.
 12. Thedevice of claim 11 wherein each mating feature is a dovetail feature.13. The device of claim 11 further comprising: d) a second upper spacerhaving a lower surface having a seventh mating feature, and an uppersurface having a eighth mating feature, and a side surface therebetweene) a second lateral spacer having an inner side surface having a ninthmating feature, an outer side surface having a tenth mating surfacetherebetween, and an upper surface therebetween, wherein the fourthmating feature of the first upper spacer slidably mates with the seventhmating feature of the second upper spacer, and wherein the sixth matingfeature of the first lateral spacer slidably mates with the ninth matingfeature of the second lateral spacer.
 14. The device of claim 13 furthercomprising: f) a third upper spacer having a lower surface having aneleventh mating feature, an upper surface disposed at an angle to itslower surface, and a side surface therebetween, wherein the third upperspacer is disposed above the second vertical spacer.
 15. The device ofclaim 14 wherein the eleventh mating feature of the third verticalspacer is located substantially directly above the eighth mating surfaceof the second vertical spacer.
 16. The device of claim 11 wherein thelower surface of the base block has a seventh mating feature, andfurther comprising: d) a first lower spacer having an upper surfacehaving an eighth mating feature, a lower surface having a ninth matingfeature, and a side surface therebetween.
 17. The device of claim 11wherein the base block has a second side surface having a seventh matingsurface, and further comprising: d) a second lateral side spacer havingan inner side surface having a eighth mating feature, an outer sidesurface having a ninth mating feature, and an upper surfacetherebetween.